1. Technical Field
The present invention generally relates to a hard disk drive, and more particularly, relates to a method of selecting a zone lay-out of a hard disk drive using zone-bit recording.
2. Related Art
Transducer head and recording media are the most important components of a hard disk drive, and the quality of hard disk drives depends on the head performance. In general, at least four heads are provided for each hard disk drive. These heads meet the basic head specifications, and there is little difference in the performance of each of the heads. This results from a change in load force during head stack swaging or a warping created when joining its base plate and cover together during the manufacture of hard disk drive. There is a little difference in the heights of the flying heads, which may affect the head performance. Generally, fifty or sixty of every one hundred hard disk drives contain magnetic heads that satisfy the head specifications, and the remainder of disk drives may have one or two heads of low performance. The disk drives with one or two heads of low performance fail to satisfy the system's error rate specifications, and as a result, they are considered to be inferior products. High-capacity hard disk drives with four heads may experience this problem as well.
Transducer heads that are defective during the manufacturing process should be replaced with new ones through reprocessing. However, since a typical defective head is firmly joined to a head stack by ball swaging, any replacement effort of only the defective head can be complicated and laborious. For this reason, the entire head stack containing a defective head must be replaced with a new one, and the heads of good quality must be discarded together with the defective head. I have observed that this requirement lowers the productivity and increases the production cost of a head assembly. Accordingly, an alternative means to retain a valuable head stack containing some defective heads can be still contemplated.